Apples and oranges. (platforms and demographics are different - MP8 was also the first MP on Wii. Compare sales to MP9 and MP7.) Further, Portal was only mildly innovative. Portal 2 was simply not innovative at all.
Meanwhile, that comparison bloody well does illustrate the diseased thinking that's led to the problem in the first place. Portal, and even Portal 2 made a lot of money.
THAT'S OKAY. IT'S OKAY TO MAKE A LOT OF MONEY.
The problem is that it's not good enough in the eyes of far too many people. These people don't want to make a lot of money. They want ALL THE MONEY IN THE WORLD, and they want it yesterday. All competitors must be ground into dust, their houses murdered and their families burned, etc, etc.
Meanwhile, who is asking Mario Party to innovate? Do you believe that Nintendo has made no innovations during the 17 years of Mario Party's 10 iterations?